1. Field of the Invention
The present invention relates generally to a vehicle suspension and more specifically to a vehicle suspension system which reduces the loss of ride and associated stability characteristics during vehicle pitching.
2. Description of the Prior Art
JP-A-62-218209 discloses a suspension arrangement of the nature disclosed in FIGS. 8-10. As shown in FIG. 8, the front and rear suspensions 2, 3 of the vehicle 1, comprise so called A-arm type upper and lower links 4U, 5U, 4L, 5L. These arms are arranged at suitable angles with respect to the longitudinal axis of the vehicle in a manner such that the front suspension 2 defines an anti-diving geometry while the rear suspension defines an antilifting geometry. This arrangement defines an instantaneous center of rotation for the front suspension at a location, which is illustrated in FIG. 8, is low and well rear of the vehicle; and a corresponding center 7 for the rear suspension which is located rear of the vehicle center of gravity 8 and forward of the rear suspension.
As shown in FIG. 9, the rear suspension is such that the pivot points (i.e. ball joints which interconnect the links with the rear road wheel 9R) defined at the outboard ends of the upper and lower links 5U and 5L, are arranged with respect to and spaced from the instantaneous center of rotation 7 of the rear suspension as indicated by lines l1 and l2: A similar arrangement is establised for the front suspension.
Accordingly, if we consider the oscillation of the front and rear suspensions, it can be considered that the wheel centers of the front and rear road wheels 9F, 9R are respectively connected to the instantaneous centers of rotation 6 and 7 by (imaginary) links.
However, with this type of suspension arrangement, as the instantaneous center of rotation 6 is located low and well to the rear of the vehicle chassis and the instantaneous center of rotation 7 is located between the center of gravity 8 of the vehicle and the center of the rear wheel 9R, the vertical displacement of the center of gravity 8 tends to become quite large and thus tends to deteriorate the ride and stability characteristics of the vehicle during vehicle pitching.
That is to say, if the vehicle is viewed from the side, it is possible to envisage a model of the nature depicted in FIG. 10. In the system depicted in this figure, the wheel centers O of the front and rear wheels 9F, 9R are fixed and the movement of the line L which passes through the centers of instantaneous rotation 6, 7 depicts the movement of the vehicle center of gravity. Further, 6a and 7a and 6b and 7b depict the positions assumed by the instantaneous centers of rotation when the vehicle undergoes forward and rear inclinations respectively. Accordingly, the link L undergoes inclination, and the vehicle center 8 of gravity which is located at a fixed predetermined location with respect to line L, is induced to move. As will be appreciated from this figure, with this prior art type of suspension configuration, the vertical displacement of the vehicle center of gravity 8 is quite large when the vehicle undergoes pitching and degrades the ride experienced by those onboard the vehicle.